The present invention relates generally to circuits used to control current levels in connected loads and, more particularly, to current control circuits which not only control current levels in connected loads but also limit the power delivered to such loads. The present invention is particularly applicable to active loads, used for example to test alternators or other power generators; however, it is also generally applicable to regulate and control the operation of other loads such as arc discharge lamps which require both current regulation and power limiting.
A variety of circuits exist in the prior art for current control and/or power limiting in circuit loads. For power limiting, both analog and digital techniques have been applied. Multiplier circuits are commonly used for analog power limiting to multiply signals representative of current by signals representative of voltage and thereby calculate power level signals which are then used to control current and/or voltage to limit power within a load. Unfortunately, such analog power limiter circuits require a substantial amount of circuitry such that a simpler design is desirable.
For digital power limiting, current and voltage signals are converted from analog to digital form and used by a processor to multiply and accumulate power levels being dissipated in a load. The accumulated power levels are then used to control current and/or voltage to limit power within a load. Unfortunately, such digital power limit circuits require substantial software and computing overhead.
Accordingly, there is a need for an improved power limiting circuit. Preferably, such a circuit would provide not only power limiting but also current control in a simplified design for regulating and controlling the operation of loads which require both current regulation and power limiting.